Colin Sebastian of Robert W. Baird says FB’s lack of any forecast is likely spooking investors, who already bid down the shares more than 8% during the regular session, following disappointing results from Zynga. More on Sebastian’s take.

Zuck at the conference call: Will he or won’t he (show up). The all-important issue of CEO Mark Zuckerberg’s decision to take part in the quarterly call is about to be addressed. The call is scheduled to get underway in about 5 minutes.

Chief operating officer Sheryl Sandberg takes over the call, focusing on the company’s advertising business. “We offer marketers the ability to reach a mass or a targeted audience and establish real and ongoing relationships directly with their customers,” she says.

Ebersman says payments revenue “essentially flat” in last three consecutive quarter, as more gamers move to mobile devices. This is a big read-through from Zynga’s disappointing results on Wednesday. “We believe this trend is due to the fact that gaming in general has been growing mainly on mobile devices, where our payment system is generally not utilized,” he said.

Spending likely to continue growing. Ebersman says “hiring top talent is a key priority” at the company. Says the company expects operating expenses “to continue to increase significantly relative to our spend in the second half of last year,” and probably at “a slightly higher growth rate” than in the second quarter. This is about all Facebook is giving in terms of a forward-looking forecast.

Zuckerberg asked about overall size of the company. He says Facebook has always been “significantly smaller” than peers on a comparative user basis. Adds that more consumer products gain a social element, that “over time, it might make sense to build more of these things ourselves,” in a possible hint that the company might be considering building its own devices. Current rumors are that the company is working with HTC to build its own smartphone.

Sandberg says “fewer than half our ads are social,” and notes that the company is “very focused” on increasing this number. Says social ads have “higher engagement rates and much higher ROI,” or return on investment, for advertisers. “So driving up that percentage is really important for us,” she says.

Analyst asks Zuckerberg about Instagram acquisition. Zuckerberg says strategy “has primarily been to buy companies for talent.” He cites Facebook’s “very entrepreneurial culture, where we want the type of people inside the company to take risks and be the type of people whowould want to build out whole companies on their own.” Says that will continue to be the case going forward.

Zuckerberg talks about the company’s approach to building a platform for various types of industries, and suggests that Facebook’s share of revenues over that platform may vary, as the company tries to estimate the value “that we’re helping to provide” for different areas. “So in gaming, for example, we think that we’re helping to provide a lot of the value, so we end up getting a relatively high percentage of the revenue that comes into those companies,” he says, adding that this percentage may be less for the music category.

Call concludes. Sandberg gets in last word about company’s approach to building its platform. Adds that a key measurement used by the company is how many developers are building on the platform. “We focus a lot on how many developers out there are using our tools, how many of the apps that are growing quickly, and how many of the services that are growing quickly are using tools like open graph as well as ads so that we can build an ecosystem.”